JP2008178786A - Countermeasure at the time of absorbent slurry concentration rising in flue gas desulfurizer - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a countermeasure at the time of adsorbent slurry concentration rising in a flue gas desulfurizer for absorbing and removing a sulfur oxide in a flue gas by bringing an absorbent slurry into contact with a flue gas, which restores the adsorbent slurry concentration to the range of proper values promptly and efficiently when the adsorbent slurry concentration rises. <P>SOLUTION: The countermeasure when the operation standard value in the adsorption tower (70, 80) exceeds a predetermined range comprises the step of automatically adjusting the amount of ash dust from the flue gas (A) to be incorporated into the flue gas desulfurizer (gas-liquid contact apparatus 10), the step of increasing the circulation amount of the absorbent slurry (increase of the moving blade divergence of a circulation pump 74), the step of increasing the oxidized air flow rate supplied into the absorption tower (increase of the oxidized air flow rate by means of an air supply means 61), the step of decreasing the absorbent slurry flow rate to be supplied into the absorption tower (decrease of the flow rate of the slurry pump 50) and the step of increasing the absorbent slurry flow rate to be supplied into a dehydrator 30 (belt filter) (increase of the flow rate of an extraction pump 20). <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

  The present invention relates to a method for dealing with an increase in the concentration of an absorbent slurry in a flue gas desulfurization apparatus, and particularly in an exhaust gas desulfurization apparatus that absorbs and removes sulfur oxides in flue gas by bringing the absorbent slurry into contact with flue gas. Flue gas that can return the absorbent slurry concentration in the absorption tower to the normal range quickly and efficiently when the concentration of the absorbent slurry in the tower rises and there is a possibility that the flue gas desulfurization unit cannot operate normally. The present invention relates to a method for dealing with an increase in absorbent slurry concentration in a desulfurization apparatus.

  In recent years, air pollution due to the influence of exhaust gases from various plants and automobiles has become serious. For this reason, the Air Pollution Control Law has been enacted for the purpose of protecting the health of the people and preserving the living environment with regard to air pollution. Each local government also establishes regulations and outlines for air pollution prevention and regulates the amount of air pollutants emitted.

  In response to this, each company is striving to protect the environment by minimizing the emission of air pollutants. For example, in a power plant with a boiler unit, air pollutants such as soot, NOx, SOx, etc. contained in the flue gas from the boiler unit in order to comply with environmental standards stipulated in the Air Pollution Control Act and pollution control agreements, etc. The exhaust is sufficiently removed and clean exhaust is performed.

  In particular, since SOx has a significant impact on the environment, it is an important duty to operate the flue gas desulfurization apparatus stably. Under such circumstances, conventionally, various techniques for efficiently removing SOx by operating a flue gas desulfurization apparatus stably have been disclosed.

  For example, in JP-A-6-238126, “Abnormality diagnosis apparatus for wet flue gas desulfurization apparatus” (Patent Document 1), gypsum quality is constantly monitored by diagnosing factors that affect gypsum quality. A technique for supporting the optimum operation amount of various components to maintain is disclosed.

  This "abnormality diagnosis device for wet flue gas desulfurization device" described in Patent Document 1 makes sulfur-oxide in exhaust gas discharged from a combustion device such as a boiler gas-liquid contact with an absorbent slurry for absorption tower circulation. The present invention relates to a wet flue gas desulfurization apparatus for absorbing and removing. This “wet flue gas desulfurization apparatus abnormality diagnosis apparatus” supports the operation amounts of various optimum components for maintaining the quality of gypsum by the following procedure.

That is, the HCL concentration and the HF concentration are calculated by inputting the coal supply amount signal, the coal property signal, and the exhaust gas flow rate signal to the exhaust gas property calculator. Subsequently, the signal, the inlet SO ₂ concentration signal, the outlet SO ₂ concentration signal, the inlet dust concentration signal, the absorbent slurry flow signal, the absorption tower extraction flow signal, the oxidizing air flow signal, the absorption tower level signal, and the calculator The calculated HCL concentration and HF concentration are input to the liquid property calculator to calculate the CaCO ₃ concentration, CaSO ₃ .1 / 2H ₂ O concentration, CaSO ₃ .2H ₂ O concentration, impurity concentration, and CaF ₂ concentration in the absorbing solution. . Subsequently, the gypsum purity calculator calculates the gypsum purity from the calculated liquid properties of the calculator, and the abnormality diagnosis device performs evaluation diagnosis of the gypsum purity. Subsequently, when it is determined that the gypsum purity is abnormal, the operation amount (absorbent slurry flow rate, oxidizing air flow rate, sulfuric acid flow rate) for returning to the normal state is output to the control device.

Further, in Japanese Patent Laid-Open No. 11-244646 “Absorbent slurry flow rate control method and apparatus for flue gas desulfurization apparatus” (Patent Document 2), in the unlikely event that the absorption liquid circulation amount in the absorption tower is maximum, absorption Even when the flow rate of the exhaust gas introduced into the tower transiently rises above the planned value, a technique is disclosed that can maintain the desulfurization rate and suppress the absorption tower outlet SO ₂ concentration below the regulation value. ing.

In the “method and apparatus for controlling the amount of absorbent slurry in the flue gas desulfurization apparatus” described in Patent Document 2, all of the circulation pumps in the absorption tower are operated, and the activity of the absorbent is reduced. in not state, the absorption tower outlet sO ₂ concentration is high set concentration or more, or at the time of the desulfurization rate abnormality became less low setting desulfurization rate, temporarily increases the set pH value, the setting absorbent slurry flow rate increases The opening command is output from the controller to the flow rate adjustment valve so that the absorbent slurry flow rate becomes equal to the set absorbent slurry flow rate. According to this "method and apparatus for controlling the flow rate of the absorbent slurry in the flue gas desulfurization apparatus", the flow rate of the exhaust gas introduced into the absorption tower should be transient in the state where the circulation amount of the absorption liquid in the absorption tower is maximum. Even if it exceeds the planned value, the desulfurization rate can be maintained and the absorption tower outlet SO ₂ concentration can be kept below the regulation value.

JP-A-6-238126 JP 11-244646 A

  However, the “wet flue gas desulfurization device abnormality diagnosis device” described in Patent Document 1 is a technology related to a flue gas desulfurization device called a grid tower, and this technology is directly referred to as a liquid injection tower. It cannot be applied to smoke desulfurization equipment.

  In addition, the “method and apparatus for controlling the flow rate of absorbent slurry in the flue gas desulfurization apparatus” described in Patent Document 2 has a plurality of circulating pumps in the absorption tower operated, and the activity of the absorbent is reduced. This is not a technique that can be applied when there is a possibility that the concentration of the absorbent slurry increases in the absorption tower and the flue gas desulfurization apparatus cannot be operated normally.

  The present invention has been proposed in view of the above-described circumstances, and in the flue gas desulfurization apparatus that absorbs and removes sulfur oxides in the flue gas by contacting the absorbent slurry and the flue gas, the concentration of the absorbent slurry in the absorption tower. If there is a possibility that the flue gas desulfurization unit cannot be operated normally due to an increase in the concentration, the absorbent slurry in the flue gas desulfurization unit can return the absorbent slurry concentration in the absorption tower to the normal range quickly and efficiently. An object is to provide a method for dealing with an increase in concentration.

The method for dealing with an increase in the concentration of the absorbent slurry in the flue gas desulfurization apparatus according to the present invention has the following characteristics in order to achieve the above-described object.
That is, the method for dealing with an increase in the concentration of the absorbent slurry in the flue gas desulfurization apparatus according to the present invention is to absorb in the flue gas desulfurization apparatus that absorbs and removes sulfur oxide in the flue gas by bringing the absorbent slurry and the flue gas into contact with each other. This is a response method when the absorbent slurry concentration rises in the tower, and automatically adjusts the amount of dust removal from the flue gas to be taken into the flue gas desulfurization device when the operation reference value in the absorption tower exceeds the specified range. A step of automatically adjusting the amount of absorbent slurry circulating, a step of automatically adjusting the flow rate of oxidizing air supplied to the absorption tower, a step of reducing the flow rate of absorbent slurry supplied to the absorption tower, and a supply to the dehydrator It is characterized in that the state of increasing the absorbent slurry concentration in the absorption tower is eliminated by performing at least one of the process of optimizing the absorbent slurry concentration comprising the step of increasing the flow rate of the absorbent slurry. It is intended.

  A method for dealing with an increase in the concentration of the absorbent slurry in the flue gas desulfurization apparatus is characterized in that a calcium carbonate slurry using limestone as a solute and water as a solvent is used as the absorbent slurry.

  In this case, the step of increasing the flow rate of the absorbent slurry supplied to the dehydrator is performed by controlling the flow rate of the extraction pump that supplies the absorbent slurry to the dehydrator according to the concentration of the absorbent slurry in the absorption tower. It is characterized by performing at least one of a step of adjusting the absorbent slurry flow rate and a step of adjusting the absorbent slurry flow rate by increasing the number of dehydrators to be operated.

  According to the method for dealing with an increase in the concentration of the absorbent slurry in the flue gas desulfurization apparatus according to the present invention, the amount of dust removal from the flue gas, the circulation amount of the absorbent slurry, the flow rate of the oxidized air, the flow rate of the absorbent slurry, and the supply to the dehydrator If the absorbent slurry concentration increases in the absorption tower and there is a possibility that the flue gas desulfurization unit cannot operate normally, the absorbent slurry concentration in the absorption tower is quickly and efficiently adjusted. It can be within the range of appropriate values. This makes it possible to contribute to environmental protection by keeping the desulfurization capacity in the flue gas desulfurization apparatus above a predetermined value and discharging clean exhaust gas that meets environmental standards and the like.

Hereinafter, with reference to the drawings, an embodiment of a method for dealing with an increase in absorbent slurry concentration in the flue gas desulfurization apparatus according to the present invention will be described.
In the flue gas desulfurization apparatus, desulfurization is performed from exhaust gas by causing the following reactions (1) to (3).
That is, in the absorption tower (see FIG. 1),
SO ₂ + H ₂ O → H ⁺ + HSO ₃ ⁻ (1)
Furthermore, in the tank (see FIG. 1), H ⁺ + HSO ₃ ⁻ + 1 / 2O ₂ → 2H ⁺ + SO ₄ ²⁻ (2)
2H ⁺ + SO ₄ ²⁻ + CaCO ₃ + H ₂ O → CaSO ₄ .2H ₂ O + CO ₂ (3)
As a result of this reaction, the final product calcium sulfate (CaSO ₄ : gypsum) is produced.

By the way, in order to remove SO ₂ in the exhaust gas with the flue gas desulfurization apparatus, a necessary amount of absorbent slurry (limestone slurry) must be introduced in accordance with the concentration of SO ₂ . In a normal case, the amount of the absorbent slurry to be charged is determined based on the measurement result in the calcium carbonate concentration meter (pH meter). However, if an unexpected situation occurs, such as the calcium carbonate concentration meter malfunctioning, and an excessive amount of absorbent slurry is introduced over a long period of time, the concentration of the absorbent slurry in the absorption tower increases. And if the concentration of the absorbent slurry in the absorption tower rises, normal operation of the flue gas desulfurization device will occur, such as clogging the absorption tower instrument pipe, decreasing the gypsum purity, and clogging the filter cloth of the dehydrator There is a risk that it will not be possible.

  The method for dealing with an increase in the concentration of the absorbent slurry in the flue gas desulfurization apparatus according to the present invention is quick and efficient when there is a possibility that the concentration of the absorbent slurry in the absorption tower increases and the flue gas desulfurization apparatus cannot be operated normally. This is often a technique for returning the concentration of the absorbent slurry in the absorption tower to the normal range.

<Smoke flue gas desulfurization equipment>
FIG. 1 is a schematic diagram of a flue gas desulfurization apparatus to which a method for dealing with an increase in calcium sulfite concentration according to an embodiment of the present invention is applied.
The flue gas desulfurization apparatus to which the method for dealing with an increase in the concentration of calcium sulfite according to the embodiment of the present invention is an apparatus for bringing the absorbent slurry into gas-liquid contact with the flue gas as shown in FIG. Air supply means 61 for contacting is provided.

  The gas-liquid contact device 10 includes a tank 60 to which an absorbent slurry (for example, calcium carbonate slurry using limestone as a solute and water as a solvent) is supplied, an introduction side absorption tower (contact treatment tower) 70, and a discharge side An absorption tower 80.

  The introduction side absorption tower 70 extends upward from one side of the tank 60 and has a flue gas introduction part 71 for introducing untreated flue gas A formed at its upper end. Smoke flows downward.

  The outlet side absorption tower 80 is extended upward from the other side part (right side in the drawing) of the tank 60, and a smoke exhausting part 81 for leading the processed exhaust gas B is formed at the upper end thereof. Thus, the flue gas passing through the introduction side absorption tower 70 and passing through the upper part of the tank 60 flows upward.

  The introduction side absorption tower 70 is provided with a spray pipe 72. The spray pipe 72 is formed with a plurality of spray nozzles 73 for injecting the absorbent slurry upward in a liquid column shape. . In addition, a circulation pump 74 that blows up the absorbent slurry in the tank 60 is connected to the tank 60, and the absorbent slurry is sent to the spray pipe 72 through the supply header 75 and sprayed from each spray nozzle 73. It has come to be.

  Further, a mist eliminator 82 for collecting and removing the accompanying mist is provided at the rear portion of the outlet side absorption tower 80. The mist collected by the mist eliminator 82 is returned directly into the tank 60 by, for example, dropping in the outlet side absorption tower 80.

  Although not shown in detail, a plurality of spray pipes 72 are arranged in parallel across the entire lateral direction inside the introduction side absorption tower 70, and the other end side of the spray pipe 72 is a plurality in the longitudinal direction of the supply header 75. Connected to each location.

  The supply header 75 has a tapered shape with a diameter reduced toward the closed one end side in a range where the spray pipe 72 is connected. The rate of decrease in the flow path cross-sectional area of the supply header 75 is set so that the internal average flow velocity is substantially constant in the longitudinal direction.

  An air supply means 61 is provided in the tank 60, and the absorbent slurry blown up from the spray nozzle 73 flows down while absorbing sulfurous acid gas and blows in using the air supply means 61. It is oxidized by air and produces gypsum.

  The air supply means 61 in the present embodiment is an arm rotation type, and includes an arm 63 that rotates horizontally by a motor (not shown) supported in the tank 60 using a hollow rotation shaft 62, and a hollow rotation. An air supply pipe 64 extending from the shaft 62 and having an open end extending below the arm 63 and a rotary joint 65 for supplying the proximal end side of the hollow rotary shaft 62 to the air source are provided. In this air supply means 61, the hollow rotary shaft 62 is rotated while the air C is being press-fitted from the rotary joint 65, and the air C is supplied from the air supply pipe 64 to the gas phase region generated on the rear side in the rotation direction of the arm 63. Further, the vortex force generated by the rotation of the arm 63 causes a tearing phenomenon at the end of the gas phase region to generate a large number of substantially uniform fine bubbles and absorbs the sulfurous acid gas in the tank 60 and the air. And come to contact efficiently.

  Then, the slurry in the tank 60 (in which a small amount of limestone that is gypsum and an absorbent is suspended or dissolved) is sucked out by the extraction pump 20, sent to the dehydrator 30, and filtered by the dehydrator 30. , Gypsum with a low water content (for example, about 10% water content). On the other hand, the filtrate from the dehydrator 30 is sent to the slurry tank 40, limestone is added together with makeup water, and is supplied again into the tank 60 by the slurry pump 50 as an absorbent slurry.

<Measures to be taken when absorbent slurry concentration increases>
Hereinafter, with reference to FIG. 2, the procedure of the response method at the time of the absorbent slurry density | concentration raise which concerns on embodiment of this invention is demonstrated. FIG. 2 is a flowchart showing a procedure of a method for dealing with an increase in the concentration of the absorbent slurry according to the embodiment of the present invention.

  In the method for dealing with an increase in the concentration of the absorbent slurry according to the embodiment of the present invention, as shown in FIG. 2, the absorbent slurry concentration in the absorption tower is monitored based on the meter indication value, and the indication value of the absorbent slurry concentration is It is determined whether or not it has risen (S1). In the present embodiment, in an ordinary case, the operation is performed such that the meter indication value of the absorbent slurry concentration is 20%. However, when the normal operation value is exceeded, there is a concern that the meter piping is blocked. Therefore, when the state in which the meter instruction value is 23%, for example, continues, the absorbent slurry concentration optimization step is performed.

Here, when the indicated value of the absorbent slurry concentration rises, the dust concentration is automatically adjusted (S2), the absorbent slurry circulation amount is automatically adjusted (S3), and the absorbent slurry flow rate to be supplied to the absorption tower is set. Decrease (S4).
In the automatic dust concentration adjustment process, the electric dust collector installed upstream of the absorption tower is automatically operated to remove the dust contained in the exhaust gas sent to the absorption tower and lower the dust concentration at the absorption tower entrance. Perform the operation. Moreover, in the automatic adjustment step of the absorbent slurry circulation amount, for example, the absorbent slurry circulation amount is changed by automatically adjusting the moving blade opening of the circulation pump. In the step of adjusting the absorbent slurry flow rate, for example, the absorbent slurry flow rate is set to about 5.0 t / h to 8.0 t / h, which is the minimum necessary for desulfurization. As described above, in this step, the concentration of the absorbent slurry is controlled by controlling the flow rate of the slurry pump for supplying the absorbent slurry to the absorption tower and adjusting the flow rate of the absorbent slurry to be supplied to the absorption tower. Try to be an appropriate value.

Subsequently, the oxidizing air flow rate is adjusted (S5). In this embodiment, limestone is used to remove SO ₂ in the exhaust gas. However, calcium sulfite (CaSO ₃ ) is first generated in the course of the reaction, and this calcium sulfite is oxidized to form a final product. A certain gypsum (CaSO ₄ ) is produced. Therefore, in order to efficiently oxidize calcium sulfite to obtain gypsum which is the final product, oxidized air is supplied using an air supply means. In the normal state, the flow rate of the oxidized air is controlled by ORP (Oxidation Reduction Potential), and the potential of the absorbent slurry in the absorption tower is measured, and the supply amount of oxidized air is increased or decreased to a predetermined value. It is done by.

  Subsequently, the absorbent slurry flow rate supplied to the dehydrator (belt filter) is increased (S6). In this step, the absorbent is controlled by controlling the flow rate of the extraction pump for supplying the absorbent slurry to the dehydrator and improving the liquid quality in the absorption tower by replacing the absorbent slurry present in the absorption tower. Try to optimize the slurry concentration.

Here, it is determined whether or not the indicated value of the absorbent slurry concentration has decreased (S7). If the absorbent slurry concentration has decreased, the processing is terminated assuming that the absorbent slurry concentration has returned to an appropriate value.
On the other hand, when the concentration of the absorbent slurry does not decrease, the number of the dehydrators to be operated is increased (S8), thereby further replacing the absorbent slurry present in the absorption tower to improve the liquid quality in the absorption tower. By trying to optimize the absorbent slurry concentration. In addition, although one dehydrator is operated in a normal operation state, in this process, another dehydrator is added and a total of two dehydrators are operated to exist in the absorption tower. Optimize absorbent slurry concentration.

  Also, if the absorbent slurry concentration is not optimized even if the flow rate of the absorbent slurry supplied to the dehydrator (belt filter) is increased, or if it takes time until it is optimized, the dehydrator with the extraction pump is used. It is preferable to stop the supply of the absorbent slurry (S9). In this process, a large amount of absorbent slurry is temporarily received from the extraction pump into the reserve tank in a short time, and a portion corresponding to the tank reception (decrease) is injected into the liquid chamber in a large amount for dilution. By trying to improve the liquid quality, try to lower the concentration of the absorbent slurry. Note that stopping the supply of the absorbent slurry to the dehydrator means that the production of gypsum is stopped.

  In addition, the specific numerical value shown by embodiment mentioned above is an example, Each numerical value is changed suitably according to the shape and scale of a flue gas desulfurization apparatus to which this embodiment is applied, the scale of a plant, an operating state, etc. Of course, it can be implemented.

  The countermeasure method when the concentration of the absorbent slurry in the flue gas desulfurization apparatus according to the present invention is increased is mainly to absorb the sulfur oxide in the flue gas by bringing the absorbent slurry used in a power plant or the like into contact with the flue gas. In the case of the flue gas desulfurization device to be removed, if there is a possibility that the concentration of the absorbent slurry in the absorption tower will rise and the normal operation of the flue gas desulfurization device will not occur, the absorbent slurry concentration in the absorption tower will be within the normal range quickly and efficiently. It can be used when returning to the inside.

It is a schematic diagram of the flue gas desulfurization apparatus to which the response method at the time of the absorbent slurry concentration rise which concerns on embodiment of this invention is applied. It is a flowchart which shows the procedure of the response method at the time of the absorber slurry density | concentration raise which concerns on embodiment of this invention.

Explanation of symbols

10 Gas-liquid contact device 20 Extraction pump 30 Dehydrator (belt filter)
40 Slurry tank 50 Slurry pump 60 Tank 61 Air supply means 62 Hollow rotating shaft 63 Arm 64 Air supply pipe 65 Rotary joint 70 Introduction side absorption tower (contact treatment tower)
71 Smoke exhaust introduction part 72 Spray pipe 73 Spray nozzle 74 Circulation pump 75 Supply header 80 Outlet absorption tower 81 Smoke exhaust part 82 Mist eliminator

Claims (3)

In a flue gas desulfurization apparatus that absorbs and removes sulfur oxides in flue gas by bringing the absorbent slurry and flue gas into contact with each other, a method for dealing with an increase in the concentration of the absorbent slurry in the absorption tower,
When the operation reference value in the absorption tower exceeds the specified range,
A process for automatically adjusting the amount of dust removal from the flue gas to be taken into the flue gas desulfurization unit;
A process of automatically adjusting the amount of absorbent slurry circulation;
A process of automatically adjusting the flow rate of oxidizing air supplied to the absorption tower;
Reducing the flow rate of the absorbent slurry supplied to the absorption tower;
It is characterized by eliminating the rising state of the absorbent slurry concentration in the absorption tower by performing at least one of the steps of optimizing the absorbent slurry concentration comprising the step of increasing the flow rate of the absorbent slurry supplied to the dehydrator. To cope with an increase in the concentration of absorbent slurry in a flue gas desulfurization system.   The method for dealing with an increase in the concentration of the absorbent slurry in the flue gas desulfurization apparatus according to claim 1, wherein a calcium carbonate slurry using limestone as a solute and water as a solvent is used as the absorbent slurry. The step of increasing the flow rate of the absorbent slurry supplied to the dehydrator is as follows:
Adjusting the absorbent slurry flow rate by controlling the flow rate of the extraction pump that supplies the absorbent slurry to the dehydrator according to the absorbent slurry concentration in the absorption tower;
The at least one of the step of adjusting the flow rate of the absorbent slurry by increasing the number of dehydrators to be operated is performed when the concentration of the absorbent slurry in the flue gas desulfurization apparatus is increased. How to respond.

Images